PROJECT SUMMARY/ABSTRACT One of the most effective interventions for smoking cessation is contingency management (CM), in which financial incentives are used to reinforce abstinence. However, traditional, clinic-based CM is not widely available because of concerns about feasibility, acceptability, and long-term effectiveness. Digital technology is now facilitating the emergence of CM formats that are likely to be more feasible, acceptable, and effective at promoting long-term abstinence. In this SBIR Fast Track application, we are proposing to complete development and evaluate the effectiveness of a digital CM program for smoking cessation: QuitBet. QuitBet is modeled upon and builds upon the commercial success of DietBet, our first product. All of our products, which we call games, combine social gaming elements with participant-funded financial incentives in the form of a deposit contract. Our ?players? deposit (we call it their ?bet?) a specified amount of their own money into the game's ?pot.? All ?winners? who achieve the game's goal split the pot equally, such that their bet is fully refunded plus they receive extra money from the forfeited bets of players who did not meet the goal. We recently developed the QuitBet prototype and conducted an initial test game with 32 players. QuitBet players made a $30 deposit. All players were mailed a portable, smartphone-connected CO testing device. QuitBet lasted for 28 days, with the official quit date on day 8. From day 9-28 (a 20-day period), players earned back $1 of their $30 bet per day of CO-verified abstinence. All remaining bet money was pooled into the ?grand prize? pot. Players who were abstinent on at least 19 of the 20 days were declared winners and split the grand prize pot equally. During QuitBet, players posted their CO test results in a private Facebook group. They also received education about smoking cessation from a game host and interacted with other players. Fifteen of the 32 players (47%) were winners. Player feedback was very positive. Our Phase I aim is to achieve the following milestones: 1) complete development of a QuitBet smartphone application and conduct a pilot trial (N = 50) to demonstrate 2) consumer demand (i.e., feasibility) and 3) acceptability. Our Phase II aim is to conduct a randomized trial of QuitBet vs QuitBet-NS (deposit contract only, no social elements). All participants (N = 550) will be offered a second game after their first game (up to 8 weeks total game duration). We hypothesize that 7-day point prevalence abstinence rates at 1, 3, and 6 months post-quit date will be higher in QuitBet than in QuitBet-NS. We will also compare QuitBet vs. QuitBet-NS on smoking heaviness and use of smoking cessation medication and examine potential mediators of outcomes such as motivation, engagement, and satisfaction.